报告摘要：In the last 15 years, we have learned that physical vapor deposition (PVD) can prepare ultrastable and anisotropic glasses with striking material properties. Almost all of this work has been performed on single component systems. The investigation of multicomponent PVD glasses is motivated by the technological importance of co-deposited glasses of organic semiconductors for the production of organic light emitting diode (OLED) displays. For co-deposited systems, we are interested in understanding how to form stable glasses, predict anisotropic packing, and control component dispersion. In the last three years, we have investigated co-deposition of roughly a dozen pairs of molecules, utilizing components that form ultrastable glasses as pure materials.
Most of our codepositions yield ultrastable glasses (high density, high kinetic stability, low enthalpy), which generally have about the same stability as vapor-deposited glasses of the pure components. Surprisingly, this occurs even when the two components have strikingly different Tg values (Tg,A/Tg,B = 1.5); we interpret this to mean that both components are highly mobile at the free surface for depositions near 0.85 Tg,mixture. DSC measurements are a useful tool for these systems. For these mixed ultrastable systems, average molecular orientation can be predicted from single component data.
In a few cases, co-deposition results in glasses in which the components are partially segregated. For example, when DO37 is codeposited with TPD, domains from 30 – 120 nm are formed, depending upon the substrate temperature. DO37 and TPD are not miscible in the liquid state, which explains the thermodynamic driving force for domain formation. Soft x-ray scattering is a useful tool for characterizing domain formation.
报告人简介：Professor Mark D. Ediger is the Hyuk Yu Professor of Chemistry at the University of Wisconsin–Madison and an Associate Editor of The Journal of Chemical Physics. He received his Ph.D. from Stanford University in 1984 and joined UW–Madison that same year as an assistant professor, where he has remained ever since. He is internationally recognized for his influential work on glassy materials, especially supercooled liquids, polymer glasses, and ultrastable glasses formed by physical vapor deposition. His honors include the American Physical Society’s John H. Dillon Medal in 1993, the National Science Foundation’s Special Creativity Award in 2006, the American Chemical Society’s Joel Henry Hildebrand Award in 2013, and the American Physical Society’s Polymer Physics Prize in 2015.
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